No abstract

An extended decay scheme for 128 Xe has been constructed by using data from the 124 Sn( 9 Be, 5n) 128 Xe reaction at a beam energy of 58 MeV. Bands have been identified as being built on several intrinsic states, including a proposed 9/2 − [514] ⊗ 1/2 + [400] two-quasineutron configuration that forms the K π = 5 − intrinsic state at 2228 keV, and on a previously assigned K π = 8 − intrinsic state at 2786 keV. A half-life of 73(3) ns has been measured for the latter. Theoretical calculations have been performed by using the configuration-constrained blocking method based on a nonaxial Woods-Saxon potential. Large γ deformation and γ softness are predicted for the ground state and the K π = 5 − intrinsic state, whereas a nearly axially symmetric shape is predicted for the K π = 8 − two-quasiparticle configuration. The low value of the hindrance factor for the E1 transition depopulating the K π = 8 − intrinsic state is discussed in the context of analogous transitions in neighbouring N = 74 isotones.

Incomplete-fusion reactions have been used to study high-spin states in 171 Tm. Gamma-rays and conversion electrons were measured using pulsed-beam conditions for enhanced isomer sensitivity.A K π = 19/2 + , three-quasiparticle isomer was identified, with a half-life of 1.7(2) µs. The faster than expected transition rates from the isomer can be understood as being due to a chance neardegeneracy, with mixing between the isomeric state and the I π = 19/2 + member of the onequasiparticle rotational band to which it decays. The implied mixing matrix element is 12(2) eV.

No abstract

Two high-spin regularly spaced rotational bands with large dynamical moments of inertia have been identified in 175 Hf with the Gammasphere spectrometer. These new bands are very similar to the previously identified triaxial superdeformed bands in the hafnium nuclei. However, the new bands in 175 Hf have been linked into the known level scheme and thereby provide the first firm spin assignments for these structures in this region. In order to understand the new bands, theoretical calculations have been performed based on the ULTIMATE CRANKER code. The new bands in 175 Hf are deduced to be built upon highly deformed structures. No experimental evidence for triaxiality was established and this work suggests that the structure of the so-called "triaxial" superdeformed bands in the Hf nuclei may be quite different from those identified in the lighter mass Lu nuclei. Since the two highly deformed bands in 175 Hf are associated with different deformations, this work also identifies the role of the intruder orbits in polarizing the nuclear shape.